Our invention relates to stable transparent oil-in-water microemulsion concentrates consisting essentially of:
(i) water; PA0 (ii) one or more hydrophobic flavor or fragrance oils; and PA0 (iii) one or more surfactants PA0 (i) water; PA0 (ii) one or more hydrophobic flavor oils; and PA0 (iii) one or more surfactants PA0 TWEEN.RTM. 20 (Polyoxyethylene (20) Sorbitan Monolaurate) TWEEN.RTM. (is a Trademark of ICI Americas of Wilmington, Del. 19897); PA0 TWEEN.RTM. 40 (Polyoxyethylene (20) Sorbitan Monopalmitate) PA0 TWEEN.RTM. 60 (Polyoxyethylene (20) Sorbitan Monostearate) PA0 TWEEN.RTM. 80 (Polyoxyethylene (20) Sorbitan Mono-oleate); PA0 CREMOPHOR.RTM. RH 40 (Ethoxy Hydrogenated Castor Oil) (CREMOPHOR.RTM. is a Trademark of BASF Aktiengesellschaft of D-6700 Ludwigshafen, Federal. Republic of Germany); PA0 CREMOPHOR.RTM. RH 60 (Ethoxy Hydrogenated Castor Oil); PA0 GENAPOL.RTM. (Alcohol Polyglycol Ether)(GENAPOL.RTM. is a Trademark of Hoechst Aktiengesellschaft of D-6230 Frankfurt AM Main No. 80, Postfach 80, Federal Republic of Germany); PA0 Sodium Lauryl Sulphate; PA0 POLOXAMER.RTM. 407 (also known as PLURONIC.RTM. F127 and PLURACARE.RTM. F127) (Ethylene oxide-propylene oxide block copolymer having the formula: ##STR1## and an average molecular weight of 12,600)(POLOXAMER.RTM., PLURONIC.RTM. and PLURACARE.RTM. are Trademarks of BASF Corporation of Parsippany, N.J. 07054); PA0 SPAN.RTM. 20 (Sorbitan Monolaurate)(SpAN.RTM. is a Trademark of ICI Americas of Wilmington, Del. 19897); PA0 SPAN.RTM. 40 (Sorbitan Monopalmitate); PA0 SPAN.RTM. 60 (Sorbitan Monostearate); and PA0 SPAN.RTM. 80 (Sorbitan Monooleate). PA0 SPAN.RTM. s have the formula: ##STR2## (a mixture wherein R is a fatty acid moiety. TWEEN.RTM. s are polyoxyethylene-substituted SPAN.RTM. s. Reference: The Merck Index, 8th Edition, Published by Merck & Company Inc., Rahway, N.J., 1968, at pages 848, 849 and 973.
as well as a process for preparing such transparent microemulsion compositions, mouthwash compositions containing such transparent microemulsion compositions, and perfume compositions containing such transparent microemulsion compositions.
The concept of the microemulsion was introduced by Schulman and Monaague, Ann. New York Academy of Science, 1961, Volume: 92, page 366. Becher, American Chemical Society Symposium Series 448, ACS, Washington, D.C., 1991 contains two chapters covering microemulsions in foods: Chapter 1, El-Nokaly, et al and Chapter 2, Friberg, et al. The microemulsion system typically contains relatively large amounts of oil and water along with a surfactant and cosurfactant except in the case of certain hydrophobic surfactants where no cosurfactant may be: required. These systems are indicated in the prior art to form spontaneously as a result of contact between the several components.
The most characteristic difference between an emulsion and a microemulsion is the appearance of the microemulsion and the emulsion. An emulsion is turbid while the microemulsion is transparent.
Rosano, U.S. Letters Patent 4,146,499 issued on Mar. 27, 1979 discloses a method for the preparation of oil-in-water microemulsions via a four-step process: (1) a surfactant is selected which is just barely soluble in the oil phase; (2) the surfactant thus selected is dissolved in the oil to be emulsified in an amount effective to yield a fine emulsion of the emulsified oil in an aqueous phase; (3) the oil, together with its dissolved surfactant is added to the water phase and shaken or stirred; and (4) finally there is provided a second surfactant in the water phase which is somewhat more soluble in water than the first surfactant to produce a substantially clear microemulsion of oil in water. Wolf, et al, U.S. Letters Patent 4,835,002 issued on May 30, 1989 discloses microemulsions of edible oils in a matrix of water and certain alcohols which are prepared using certain edible surfactants for use in various products such as beverages. El-Nokaly, et al, U.S. Letters Patent 5,045,337 issued on Sep. 3, 1991 discloses microemulsions which are thermodynamically stable, clear and homogeneous which are made from a polar solvent, a specific polyglycerol mono, diester and a lipid. El-Nokaly, et al discloses that these microemulsions are edible, have good flavor and can be used to disperse water soluble nutrients, vitamins, flavors and flavor precursors in oils. The polyglycerol mono diester in El-Nokaly, et al consists of a mixture of mono and diesters of branched or unsaturated fatty acids having from 12 to 24 carbon atoms and a polyglycerol mixture consisting of 0% to 10% monoglycerol and other polyglycerols, 30% or less diglycerol, 25% to 50% triglycerol, 15% to 50% tetraglycerol. Tabibi, et al, U.S. Letters Patent 5,130,122 issued on Jul. 14, 1992 discloses oral cavity and dental products prepared by microemulsifying an adsorptive oil in an aqueous medium to produce uniform submicron sized droplets. It is disclosed by Tabibi, et al that the products disclosed therein avoid the generally unaesthetic, oily, and unpleasant taste problems of previous similar products.
Nothing in the prior art discloses or implies a high flavor or fragrance loading, e.g., 25% flavor or fragrance oil in a microemulsion which has unexpectedly and advantageously high stability yet is free of lower alkanols, e.g., ethyl alcohol or contains less than about 1% of lower alkanols, e.g, ethyl alcohol.